Wichita eagle., 1887-11-25
THE SIGNAL Sc RVlCE,
Some Facts About Storm Centers-Pecu-
Iiarly Difficult Problems.

liarly Difficult Problems.
New YORK, Nov 24-When the system
OF weather prediction was organized I'M
der Gen. Myer the value of the predic
tions was at once widely recognized, but
since that time the general trustworthi-
ness of the work has been such that absO-
lutte correctness was looked for in a science
that has reached little more than its first
decade of experience 1t was overlooked
that about forty ont of every 100 predic-
tons failed in 1871, and that twelve out Of
the same number failed as late as 1882
In recent years these percentages have
been lowered by the very rigid require
ments Of verifcations a decline of accu-
racv in predictions since 1884 is due to the
fact that the time covered by the pTedic-
ton was extended TO thirty-two hours.
With this increase of time from twenty
four to thirty-two hours, there has been a
diminution Of seven per cent in the sue
cessful predictions There is difference
of 49, per cent between the predictions of
the best officer and those of the poorest.
A reduced percentage in 1881 is due to
the fact that. restrictive legislation has
caused new officers TO serve their appren-
tieeship by predicting at the expense of the
country The present percentages are
lower, but the results are better than ever
before The officers have greater difficult
ties to overcome owing to the limited num-
Der of signal stations. the sharp gradients
of Temperature and the great variety Of
local peculiarities that must be kept in
mind and estimated. There is a constant
public demand for completeness, when
owing to the nature of the phenomena, it
is impossible to draw a line and prOgnOsti-
cate rain on one side OF 1t and none on the
other The correctness of the predictions
OF the Atlantic seab0ard would be i'm
proved by the presence OF signal Office
lightships in the Atlantic ocean. This
has been thought Of by the signal officers,
and the scheme definitely proposed on
three occa Sions, but was abandoned owing
to the great expense and the mechanical
difficulties. Such a system Of signal
ships would be great advantage to Eu-
rope.
Storm centers, as traced on the tri-daily
weather charts. may move with more than
double the speed calculated, or they may
remain at rest or Unexpectedly vanish.
Sometimes two storm Center5 move toward
a region from widely different directions.
Dakota and on the same chart another
may progress from the same region toward
the Mississippi valley. The velocity OF
each may vary from ten to twenty miles
an hour, depending upon the rapidity OF
the upper currents In which the disturb
ance Is moving.
Some idea OF the difficulty OF the work
may be gained by considering the fact shat
the officer must know the local peculiari-
ties of every signal station throughout the
country, and must become 50 familiar with
the weather charts tbat he can read their
indications at a glance. lie usually pre-
diets for forty different districts, for which
temperature weather and wind must be
determined. Each prediction must be
made within sixty seconds, because the
time Is strictly limited. 1t is the most
difficult and responsible work required of
any government officer An error in the
temperature prediction at certain critical
stages in the autumn may freeze up the
river traffic, causing boats to be detained
in midstream, resulting in damage amount
ing to many thousands of dollars. 4 mis-
take in a cyclone prediction might cause a
great loss of life and property along the
Atlantic coast, as well as on the lakes
Many people fail to consider what the
officers call the ''diurnal change" the tenn
perature being generally higher at p. m.
and lowest at : a. NJ, daily. Even with
good thermometers people may think
given prediction not verified because of
failure to compare il with a previous tenn
peratute at the same hour-temperature
at different hours being taken-the 3 p. m.
temperature one day being compared with
the 10 p, III. of an other day bv mistake or
through ignorance. OF course the people,
as s. rule verify predictions by their sensa-
tons of heat and cold In very marked
changes this may roughly enswer, but in a
large humber OF cases, particularly in sum
mer, the personal convictions may not be
within l5o of the thermometrcal record
owing TO the presence or absence of hu-
Nudity. With the presence Of much mos
ture in the dead calm, the sensation of neat
at So may equal that Of l00o in dry air
1t thus happens taat at times the fall of
$50 may be accompanied 10y apparently no
diminution Of heat. OF course this is ex-
ceptionGl, but it is one of the many condi-
lions that lead the public TO think at times
that the signal Office predictions are very
defective.
Predictions for Colorado. Wisconsin,
Illinois. Arkansas and the Atlantic coast
are the most difficult In regions where
most Of the storm centerS originate along
the northern range of the Rocky Noun
tains, it is far from easy to estimate the
special direction OF the storms eastward
movement As the storm ceuters leave
the Mississippi valley they become more
decisive and calCulable Lieut. Finley has
shown that storm areas advance towards
the regions of the greatest moisture. and
that the knowledge of these regions is an
important element in the predictions
Twenty-Five years ago the well-known east
wind that brings rain 10 the eastern coast
states was supposed to come from a rain
center eastward IN the ocean, but ii is not
known to blow toward rain Cauter
usually coming from Uhe, west or northwest
The signal Office weather charts first dis
PEELED the old illusion
kaSteTly winds on the Atlantic coast
lo&er the temperature. increase he humid
ity of the air and frequently give rise to
local showers, sometimes heavy. On the
approach Of any decided storm from the
west the coast winds are Of course east erly.
shifting 10 westerly IS the haromtric de
press on passes OF the coast The east
wind does not bring the storm in the sense
of causing it, for il is the approach of the
barometric depression that gives rise 10
the east wind. OF course this Is indepen-
don't of what are called land or sea brcezes.
which are merely local effects. IS winds
are the hardest TO predict. 50 temperatures
are the easiest, comparatively speaking.
The temperature Is always higher ii front
OF a storm center than in the rear Of II. In
the rear OF an area Of clear, bright weather
high barometer region the temperature
always rises slowly. These facts some
what, but not completely, simplify the
predictions of temperature. The earth's
rotation shifts nearly all great storm cen
tiers eastward. which also makes the pre-
dlcuon of temperature moro calculable.
The following officers have made preCic-
tons since 1871: Lieuts. Story. Dunwoody.
Craig, kllbourne, Greedy. Allen. Powell
Greene, MaXfield Woodruff Gl3SSfaf-J